Borax spinning bath



July 25, 1950 w, HARE ETAL 2,516,316

BORAX SPINNING BATH Filed July 14, 1949 FIZZ | I il 1 I Q IN VEN TORS WESTON A NDRE W HA RE FRANK KERR SIGNAIGO ATTORNEY Patented July 25, 1950 UNITED STATES PATE '1' cr t cs j 1 2,516,316 v 7 1 1 t BORAX SPINNING BATH Weston Andrew Hare, Kenmore, N. Y., and Frank Kerr Signaigo, Wilmingtom-DeL, assignors to E. I. du Pont de Nemours & Company, -Wil-- mington, Del., a corporation of Delaware Application July 14', 1949, Serial No. 104,53

regenerated cellulose articles and it is particularly concerned with improvements in the'art of making high tenacity rayon from viscose.

Various methods have heretofore been suggested for making rayon from viscose and a number of these processes have involved the stretching of the filaments for the purpose of improving tenacity and otherwise modifying the physical characteristics of the filaments. These pre-. viously known processes are subject however to certain limitations, particularly with respect to the degree of stretch which can be imparted to the filaments and also with respect to the inability to produce very high tenactiy yarn having the proper physical characteristics. This narrows the field of the utility of the processes and products. It has been found in accordance with the present invention that defects encountered in previous practice can be overcome by the use of novel spinning .baths and carefully controlled conditions of filament formation and treatment.

It is an object of this invention to provide a new and improved process for the manufacture of regenerated cellulose articles. A further object comprehends the production of rayon having-improved physical characteristics. An additional object pertains to the use of a special type of coagulating bath in forming regenerated cellulose products. Another object relates to the production of cellulose xanthate filaments which can be stretched to a considerable degree and which, upon regeneration, yield a product having a very high tenacity. Other objects ofthe invention will become apparent hereinafter. M

The objects of the invention are accomplished in general by extruding viscose into a bath containing dissolved therein a substantial amount of a borate, being an amount equivalent to at least 5% of borax and maintained under such conditions as to precipitate the cellulose xanthate rapidly without substantially converting it to regenerated cellulose. Thereafter the water-soluble cellulose xanthate structure is preferably stretched a very substantial amount and then converted to regenerated cellulose by the use of any suitable treatment following which the product is washed, purified and dried.

One form of apparatus, suitable for use in carrying out the process of the present invention is illustrated in the accompanying drawing.

Figure 1 is a diagrammatic, side elevational view, with parts shown in section, of an apparatus particularly desirable for operation in accordance with the description set forth in Example 1, below.

17 Claims. (Cl. 18-"54) Referring to the drawing, a viscose filament forming composition forced through candlee filter 2, goosenec 3, and spinnerette'l in the conventional manner. The filaments "6 issue from spinnerette 4 below the'surface or; the spinning bath in tank'5; From the spinnerett'ethe filaments 6 are passed about'feed wheel "1 and cooperating guide roller '8, then about rollers l0 and u positioned in the stretchingbath in tank 9,-then about feed wheel l2 and cooperating guide roller I3. The yarn is passed aboutthe tw'o feed wheels 1 and I2 with a sufficient number of turns to prevent slippage of the yarn. Feed wheel I2 is rotated at a'hig-her speed than feed wheel I so as to impart a stretch to the filaments passing through the bath in tank 9'. v

From feed wheel 12, the yarn drops of its own weight onto eccentrically revolving plate I4 to build up the yarn cake IS. The eccentrically revolving plateis ofthe type described in-U. S. Patent to Dannenberg et al. No. 2,089,159.

For convenience, the invention will be described with particularreferenceto rayon although in its broader aspects it is applicable to the manufacture of articles haVing a physical shape or form diiferentfromrayon; i v l v The following examples describe various modes of practicing the invention and in these examples, which are intended to illustrate rather than restrict the invention','parts and proportions are by weight unlessotherwise specified;

j'lllardmpleI Viscosev containing 5% cellulose and 9% -s0'= dium hydroxide" .and .having a common salt (sodium chloride) indexof 210 was extruded through a spinnerett'einto a bath prepared from 20% borax (Nal'aBaOmIOHzO), 10% sodium 'sulfate and water, towhich'is added suflicient sulfuric'acid to yield a pH of "4.0. The bath was maintained .at approximately 60 C. The fllae ments .were'ipassed'through thebath for a" distance of 6 inches without contact with guidesor any other device which may impart tension and were then withdrawn "from the bath and passed through air at normalroomconditions (7 5? F. and atmosphericpressure) for a distance. of .8, inches .to aapositivelydriven glass roller. or: feed wheel which imparts to the filaments a speed of. 300 inches per minute. -The filaments are r u he glass d wf o l ve t es to prevent slippage using grooved rollers freely mounted-to keep the yarn passesseparated, which travel therearound was equal to about inches: e fi ame we e pa sed tor a, i tance of, 20

ond bath to 3.4 times their original length, i. e their length at the first driven roller (the stretch I This second bath maih thus being 240%). tained at boiling temperature. The yarn leaving the second positively driven" roller was allowedto fall of its own weight on toa flat plate which is so moved as to traverse the yarn according-to any desired pattern and thus build upasuitable cake Or package. The filamenits o'i am seams" point were still in the form of cellulose xanthate Example H A viscose solution containing 7% cellulose and 9% sodiumhydroxide and ripened to a com r'non salt (sodium chlori'del index-of 1.8 wasextruded through a spinnerette; into bath prepared from 15% borax, 15% sodium sulfate; 5% ammonium sulfateand 65% water, together with sufiicient sulfuric acid to wield a pH o'f'4.l, the bath being maintained at atemperature of 60 C; After a bath'travel of ,6' inches 'at'no' substantial tension and anair travel of 8 inches, the yarn was passed onto the firstof two stretch= ing drums-at a; speed of 450 inches per minute. It was then led for a distance of-20 inches'through a second bath prepared from borax, 10% sodium sulfate and 80% water with suflicient sulfuric acid toyielda pH of 6.0 and maintained at a temperature of 100 G. The yarn was removed frem'this bath' by means of the second stretching drum rotating aka peripheral speed of 1,550 inches per minute; the yarn having been stretched" to a length of 3.44s'ti'rnes" its 'origii'ial length: "(244% stretch)! during its travel' througfi the -las-t bath. Theyam was further processed as'd'escribed under Example I except arege'nerating bath'prepared from '20 %2'sodiu1n sulfate, 6% sulfuric acid and 74 'water was used at '30 C; andfo'r' a :period'of luminutes. Tlfe final y'arn possessed a dry tenacity'of 5.02 grams per denier, a: wet tenacityof 3i52- grams' per denier =and"a-d-ry elongation-"of 6.4%; I I

' Ediat'riiile HI ripened to a com nsalt fsiidiriih' anion-(re) index off 334 and do use "8% cellu+ Risesna -9%" hy o de" was-extruded througn'a 'spinnefttei a guesses-eunuc prepar'eenoin 17.4%w orax; 12% 'sddimhfsul fate and 5.1% minimum sulfate and 00.3 wear and adjustd'to aZ' 15H of '453 ythf addition of suitable anteater sulfuric acid; bath being maint'a'me'd-at a temperature of 70 C. The menses passed this bath at dis-- tance of 6 inches at no substantial tension, then through air for a distance of 8 inches, around a feed wheel at a linear speed of 900 inches per minute, and through a second bath for a distance of 20 inches, the second bath being formed from an aqueous solution containing 10% borax, 10% sodium sulfate and 80% water adjusted to a pH ofv 610 with sulfuric acidand-maintained at a temperature of 100 C. The yarn was then passed around a second feed wheel driven at such a speed as to stretch the yarn about 185% cliiriii'g' its passage through the second bath. The stretched yarn. was collected in the manner anathema-Example I as umegenerated cellu- -lose Xanthate, was wrapped in a suitable cloth covering-and was regenerated by being immersed for a period of 10 minutes in a bath consisting or 20%" sodium sulfate, 6% sulfuric acid and 74% water maintained at 30 C. The regenerated yarn obtained was then passed in cake form under purifying and treating showers and finally dried. The final yarn possesseda dry tenacity of 4.08 grams per denier, a ratio'of wet to dry tenacity of 0.85, and dry and wet elongations of 9.2% and 9.1%; respectively.

Err'dmp'lelv A viscose solution ripened to a common salt (sodium chloride) index of 2:0 and containing 5.5% cellulose and 9% caustic was extruded-into an aqueous bath containing 15% borax, 15% sodium sulfate, 5% ammonium sulfate and water adjusted to a pH "of 4.5 bysuitable additions of sulfuric acid, and maintained at 60 C. After a bath travel of 6 inches-at no substantial tension, the yarn was passed for a distance of 140 inches through air and around the first stretchingroller-and-was stretched 113% through a stretchingbath of the following composition: 10%boraX, 15% sodiums'ulfa-te and water and heated to a temperature of C. The stretched ya'rn was collected in'a relaxed state as in Examplel and was regenerated by immersion for. '30 minutes inaboiling hath made up' of 30% ammonium sulfate, 10% sodium sulfate and sufiicient sulfuric acidto yield a pI-I'of 4.5. The stretched yarn after being purified and dried as described in Example lposses'sed a dry tenacityof 3:81 grams per denier, a wet tenacity' of 2.01- grams per denier, and wet anddry 'elongations of 6.0%and 632%, respectively.

' Example V -A viscose containing'5% cellulose and 9% sodium hydroxide was spun ata common salt (so-- dium chloride): index or 2 0- into a spinning bath containing approximately 18% borax, 9% sodium sulfate, 9% glucose and 62% water, adjusted to a pH of 4.0 and maintained at 57 C. After passi-n'g through 6 inch'es ofthisbath without theuse of guides, the coagulated' filaments we're withdrawn at 300 inches'per minute'and advanced in a substantially tensionles's condition through 8 inches air travel and for inch'es'around a positively'driven roller. The threadwas then subjected to high tensionand'stretched to 3.40 times its original length (240% stretch) while passing through a second bath containing approximately 10% borax and 10% sodium sulfate, adjusted to a pH of 5.6 and maintained at the boiling point. The yarn was drawn from the second bath-by a second positively driven roller at 1020 inches per minute and collected rel'aiied on a slowly ow ing table seas to form a traversed package. "The water-soluble ka'nthate yarn was-regenerated in '5 a bath of the same composition as the stretching bath, washed, finished and dried as in Example I. The final'yarn had the following physical properties:

Dry tenacity 5.34 grams per denier Wet tenacity 4.16 grams per denier Ratio of dryzwet tenacity .78 Dry elongation 6.0% Wet elongation n. 6.7% Filament crossa section smooth, uncrenulated, round Example VI A viscose containing 7.9% cellulose and 9.1% sodium hydroxide was spun at-a common salt (sodium chloride). index of 3.7-intoa spinning bath containing 17.2% borax, 17.0% sodium sulfate, 5.0% ammonium sulfate and 60.8% water, adjusted to a pH of 4.3 and maintained at 63 C. After passing through 6 inches of this bath without the use of guides, the coagulated filaments were withdrawn at 900 inches per minute and passed through 8 inches of air travel and then 130 inches around a positively driven roller. The yarn was then stretched 50% or to 1350 inches per minute while passing through a second bath containing 10% borax and 10% sodium sulfate, adjusted to a pH of 6.0 and maintained at the boiling point. The yarn was drawn from the second bath by a second positively driven roller at 1350 inches per minute and collected, relaxed on a. slowly'moving table. After regenerating, washing, finishing anddrying as previously described the yarn had the. following physical properties:

Dry tenacity grams per denier 2.16 Wet tenacity -1 do 1.14 Dry elongati'on' per cent 21.7 Wet elongation do 30.0

Example VII A viscose solution containing 8.1% cellulose and 8.85% sodium hydroxide and ripened to a common salt index of 5.0 was extruded through a spinnerette into a bath prepared from 24.3% borax 18.4% ammonium sulfate and 57.3% water and adjusted to a pH of 7.6, the bath being at a temperature of 65 C. After a bath travel of 6 inches at no substantial tension and an air travel of 8 inches, the yarn was passed to a drawoff roller at a speed of 900 inches per minute. It was then led for a distance of inches through a second bath of 9% borax, 9% sodium sulfate and 82% water maintained at a pH of 6.2 and a temperature of 95C. Theyarn was removed from this bath by means of asecond drum rotating at a peripheral speed of 2475 inches per minute, the yarn having been stretched to a length of 2.75 times its original length" (175% stretch) during its travel through the last bath. The yarn was regenerated in a bath containing 20.0% sodium sulfate, 6.0% sulfuric acid, 74.0% water at room temperature and thereafter was washed, finished and dried. The finished yarnhad a dry tenacity of 3.61 grams per denier, a wet tenacity of 2.30 grams per denier with dry and wet elongations of 7.2 and 7.6 respectively.

Example VIII Yarn was spun in ;the manner shown in Example VI but the coagulated yarn after passing ,3, passes around the initialor drawoff wheel at 900inchesper minute was-allowed to fall directly onto atraversed table forming a package. This package was wrapped in cloth and regenerated in a loath of 10% borax, 10% sodium sulfate, having a pH of 6.0 and temperature of C. The yarn was then washed, finished and dried and possessed the following physical properties.

Dry tenacity grams per denier 0.95 Wet tenacity do 0.56 Dry elongation per cent 1 21 Wet elongation do This yarn may be treated with liquid ammonia in accordance with Woodell, U. S. 2,462,927. to increase the elongation to about 250%.

The utility of the invention is dependent to a large extent on the precipitation of coagulation of the viscose independently of regeneration. The. baths utilized in the above examples under the conditions present exert a strong and rapid coagulating effect on viscose without at the same time causing'any'substantial degree of regeneration of the coagulated xanthate structure. The pH, of the coagulating bath is maintained within the range of 3.0 to 9.0 and preferably within the range of 4.0 to 6.0. The beneficial effect of the borate ions in the bath is lost if the pH is outside the range of about 3 to about 9.

The coagulating bath contains 5% or more of a borate calculated for convenience as borax (NazBrOmlOI-DO); i. e., although much of the borate may be present as boric acid, nevertheless in stating that the coagulating bath liquid contains 5% or more by weight of borate, this signi fies a weight calculation on the convenient assumption that all of the borate is present as borax. It is obvious that the borate radical may be present in other forms, for example in-the form of acid borate, hypoborate, metaborate, perborate as well as-the tetraor pyroborate and as combined with alkali metal or ammonia. Similarly the coagulating bath also contains 5% or more of sulfate preferably as the result of sodium sulfate additions but sulfates of other basesmay be used and sulfuric acid additions to adjust the pH also contribute. For convenience the sulfate is often calculated as sodium sulfate (NazSOU.

In describing the specific composition of the borate-sulfate baths utilized in the above ex. amples, it is to be understood that although the baths can be made up from commercially avail ablematerials so as to have approximately the desired pH, for instance by using boric acidor sodium bisulfate, nevertheless it is usually advisable to add a certain amount of mineral acid, 0. g. sulfuric acid or its acid salts so as to adjust the pH of the bath accurately to the desired value. In general any other acid or acidic material may be used to get the desired pH.

Although the coagulating bath can comprise, if desired, an aqueous solution containing only alkali metal salts of boric and sulfuric acids in an amount of from 5 to 20% of each and preferably acid'necessary to yield the desired pH, the bath may also contain other salts of strong acids. Thus, as indicated in Examples II, III, IV, VI and VII the bath may also contain a substantial amount of ammonium sulfate, one typical form of such bath which is preferred being an aqueous solution containing 15% borax, 15% sodium sulfate and 7% ammonium sulfate, the bath being adjusted to a pH of, for example, 4.0 to 7.6. The addition of ammonium sulfate along with sodium or other sulfates or inplace thereof is indeed important. .This ammonium sulfate addition to asrasic the spinning bath makes possible very substantial increases in speed'of'spinning as for example 2, 3 or more times the maximum speed attainable in borax-sulfate baths free of ammonium sulfate. The addition of as littleas 1 or 2% ammonium sulfate will noticeably improve the rate of spinning while 5% or or more will generally yield optimum results both in speed and qualityof yarn produced. Another material that can be added to the borate-sodium sulfate baths with advantage is glucose or other polyhydric alcohol such as glycerine or a glycol, as indicated in Example V.

The total salt concentration in the bath may range from 19% to 55% with amounts of 20% to 45% being preferred. Thus, a bath containing 40% ammonium sulfate and borax may be used. Concentrations leading to salt crystallization on guide surfaces, etc., are generally avoided.

The coagulating bath is preferably maintained at a temperature of 45 to 75 0., the yarn travel through the bath preferably being of the order of 2 inches to 18 inches. However, these temperatures and bath travels are not critical, provided only that they are not so great as to cause any substantial degree of regeneration of the cellulose xanthate structures produced therein. Since spinning requires but a few seconds, very little regeneration occurs at the higher temperature. The yarn must, however, be preferably completely coagulated before it is subjected to the subsequent stretching operation of the invention. When, as in certain of the examples, the travel through the coagulating bath is insufficient to completely coagulate the extruded viscose, it is desirable to lag the incompletely coagulated yarn under lowtension, for example, by passing it through air, for a time sufficient to complete the coagulation. Or, if desired, the yarn can be passed through a second borate-sulfate coagulating bath for a period of time sufficient to complete the coagulation. If the yarn is not completely coagulated prior to stretching, the amount of stretch obtainable will be distinctly impaired.

It is important, to obtain the full advantages of the invention, for coagulation to take place under conditions of very low tension. Thus, the tens1on imposed on the filaments in the coagulating bath should not be in excess of 0.1 gram per denier and preferably not in excess of 0.01 gram per denier. Where the viscose structure is nonfilamentary, tensions equivalent to those given in connection with filaments will be used. I The stretching of the coagulated-only yarn obtained in the course of this invention can be accomplished by passing the yarn about positively driven pairs of stretching rolls or in any other known manner. In accordance with the examples, this stretching is preferably performed while the yarn is passing through a bath of the same general type as the coagulating. bath, but heated-almost to the boil since such baths assist in developing the greatest degree of stretch. However, this is not essential. The stretching operation can, if desired, be performed in the presence of an aqueous solution of inorganicsalts, a liquid such as glycerin, triethanolamine, ethyleneglycol, etc., or even in the presence of a gaseous medium such as live steam, air, carbon dioxide, sulfur dioxide, etc. These stretching media ars preferably maintained at an elevated? temperature, for example, 100 C. or more. However, this is not critical, to the practice of the invention and they, can,.if desired, be maintained at any other temperature, for example, at room' tern per'ature." In accordance with the principles of this invention, the .yarn at the start of the stretching operation is substantially unregenerated and is water-soluble. The duration of the stretching operation and the contact of the yarn with the stretching medium is preferably so short that no substantial amount of regeneration is effected. This is not critical to the practice of the invention however and,'if desired, the yarn may be partially or completely regenerated during the stretching operation.

The stretched yarn is then collected in suitable package form and regenerated. It may be collected on a rotating bobbin in the form of a crosswoundpackage or ina centrifugal bucket of the type customarily employed in the spinning of viscose rayon yarn, or it may be collected in any other package form. Preferably, however, the yarn is permitted to fall in a relaxed, tensionless state'on toaslowly moving supportand formed into a cake-likc package in the manner of Exsample I above. The yarn package protected by a suitable cover is then treated with a regenerating bath for a suitable period of time. This bathcan comprise a mineral acid solution, for example of the type generally employed in the single bathprocess in the spinning of viscose rayonyarn and containing from 8% to 10% sulfuric acid, together with varyin amounts of inorganic salts such as sodium sulfate, etc., or it may comprise an equeous inorganic salt solution or aninert liquid (such as glycerin) heated to a high temperature, It may comprise a boiling solution of the same'general type as the coagulating or: stretching baths of this invention. Preferably, however, the regenerating bath is an acid salt bath comprised of about 6% sulfuric acid and 20% sodium sulfate maintained at a temper-ature of about 30 C. On the other hand, the yarn wet with occluded coagulating bath and stretching bath liquors can be regenerated by spontaneous decomposition of the cellulose xanthate'by permitting itto stand a suificiently long time (for example 24 hours) at room temperature. In such acase, of course, the humidity of the surrounding atmosphere should be main.- tained sufiiciently; high to 'prevent crystallization within the yarn of those salts contained in the occluded liquors. It is not necessary that the yarn be regenerated and purified in package form. The coagulatedonly yarn can be led through-a regenerating bath in a continuousv manner prior to its collection in package form, or the yarn can be collected in a relaxed, tensionless manner ona-slowly moving conveyor belt of the type shown 'in British Patent No. 379,880 to 'Iopham, the yarn, collected in the term of small overlapping ringlets, being subsequently led under showers of regenerating and purifyingliquids and dried. The invention can be applied to continuous spinning, purification and collection processes of any character.

Although any method can be used in preparing the viscose utilized in. the practice of the invention, the viscose employed in the examples was prepared by a standard method involving the combination of alkali (soda) cellulose with 26% carbon bisulficle based on the cellulose content of the alkali cellulose. Also, viscoses having a wide range of viscosities maybe used, e. g. from 64 to 960 poi'ses; Viscoses which have been submitted to a very shortor very long ripening period may be used togood advantage-as, forexample, a high saltindex; viscose. (1410 or more) or a low salt index viscose (2.0 or less) ,Thefhs'ibfth 'strdng coagulating baths -of inventionfcauses rapid coagulation'of a high index yiscos'efas well 'as' low index viscose. 'It'is lsopreferred, although not critical, that the alkalice'll'ulose" used be'; subjected only to a short aging periodgj It is preferred, 'iniorder, to develop the greatest stretchability of the coagulated,.unregenerated structures, to utilize viscose 'inwhich the caustic content is higher than the ce'uuioseccntem; e'.fg.' a viscose containing 7% cellulose andj9% sodium hydroxide. Howeve n'othe 'f viscoses whichha've a sodium hydroxide contentgless, than'the cellulose may also be used and gen lly speaking, viscoses having a cellulose or' caustic content of between 4% and 9%, or mora are quite satisfactory.

From the abovede'scription, it"is clear that the present invention makes possible the continuous rapid formation of thoroughly coagulated filaments which can be stretched so as permanently to increase their length 100%, 150%, 200% and more, this degree of extensibility being far beyond that possessed by cellulose xanthates produced according to previously known processes. Filaments and yarn formed by converting such coagulated structures to regenerated cellulose possess a ratio of wet to dry tenacity of 0.70 and higher, and possess a dry tenacity of 5.0 grams per denier and higher. The new yarns of this invention furthermore withstand severe treatments such as washing, treatment with swelling agents, etc. with little if any loss in strength.

Filaments spun in accordance with the preferred process of this invention furthermore possess a smooth, uncrenulated surface. Moreover, they resemble in their cross-sectional dimensions, the shape of the spinnerette orifices through which the viscose solution is extruded into the coagulating only bath. The size and number of holes in the spinnerettes used in the practice of the invention are not critical since any standard spinnerette, e. g. one containing 40 holes and generally of the type used in the production Of 150 denier yarn according to ordinary rayon manufacturing methods is satisfactory. such spinnerettes normally have a hole size of 0.003 inch, but is has been found, in the exercise of this invention, that a spinnerette hole size of less than 0.003 inch gives somewhat better results.

The improved coagulating baths provided by this invention not only make it possible to produce a yarn of very desirable properties, but also make possible a spinning process that is admirably adapted for use on a commercial scale. The process does not require the use of complicated apparatus or difiicultly prepared baths. Moreover, the ingredients employed are relatively inexpensive.

The invention has its principal utility in the manufacture of filaments and yarns. However, the invention, broadly speaking, is applicable also to the production of thin tubing and other types of products by the viscose process with the attaining of generally the same advantages which result from the use of the invention in the manufacture of filaments and yarns.

We claim:

1. A process which comprises precipitating viscose in an aqueous bath having a pH of 3.0 to 9.0 and containing dissolved therein salts in such an amount as to rapidly coagulate the viscose without substantially regenerating the coagulated cellulose xanthate, a portion of said salts being a borate present in amounts equivalent to at least borax.

from 10%"to 55%. 4. A process in accordance with claim] 1 in which the 'total, concentration of said; s'alts from 20% to 45%.

5. A process which comprises precipitating. vis cose in'an aqueous bath havingflapHof 3,0, to 9.0 and containing salts dissolved therein iii-such an amount as to rapidlycoagulate the viscose without substantially regeneratingQthe coagulated-cellulose xanthatein'the absence ofsub stantial' tension, 'a portion of said salt 1 beinga borate present amounts equivalent to atleast 5% borax.

6. A process which comprises precipitating viscose in an aqueous bath having a pH of 3.0 to 9.0 and containing dissolved therein salts in such an amount as to rapidly coagulate the viscose without substantially regenerating the coagulated cellulose xanthate and stretching the resultant product, a portion of said salt being a borate present in amounts equivalent to at least 5% borax.

'7. A process which comprisesprecipitating viscose in an aqueous bath having a pH of 3.0 to 9.0 and containing dissolved therein salts in such an amount as to rapidly coagulate the viscose without substantially regenerating the coagulated cellulose xanthate, a portion of said salts being a borate present in amounts equivalent to at least 5% borax; and stretching the resultant product in the presence of an aqueous medium containing dissolved therein a substantial amount of borate.

8. A process which comprises precipitating vis cose in an aqueous bath having a pH of 3.0 to 9.0 and containing dissolved therein a borate and a sulfate in such an amount as to rapidly coagulate the viscose without substantially regenerating the coagulated cellulose xanthate, stretching the resultant product and, after the streching is completed, converting the stretched xanthate to regenerated cellulose.

9. A process which comprises precipitating viscose in an aqueous bath having a pH of 3.0 to 9.0 and containing dissolved therein a borate and a sulfate in such an amount as to rapidly coagulate the viscose without substantially regenerating the coagulated cellulose xanthate, stretching the resultant product, and then converting the stretched xanthate to regenerated cellulose while in the relaxed state.

10. A process of manufacturing regenerated cellulose yarn which comprises extruding viscose into a bath having a pH of between 3.0 and 9.0 and containing dissolved therein at least 5% each of a borate and a sulfate, calculated as borax and sodium sulfate, respectively, under very low tension conditions, stretching the resultant cellulose xanthate filaments at least and converting the stretched cellulose xanthate filaments to regenerated cellulose.

11. A process of manufacturing regenerated cellulose yarn which comprises extruding viscose into a bath having a pH of between 3.0 and 9.0 and containing dissolved therein at least 10% each of a borate and a sulfate, calculated as borax and sodium sulfate, respectively, under very low tension conditions, stretching the resultant cellulose xanthate filaments at least 150%, and converting vthe stretched acellulcse xanthate filaments to regenerated .cellulose while ln the'relaxed'state. I f "12. process ofmanufacturing filaments rof regenerated cellulose which comprises extruding Viscoseunder very" low tension conditions into wa Bath having a'pH of between lio and-6=0 and containing dissolved therein at" Ieast v10% each (if aborate and asulfatecaIcuIated Las "19mm and "sodium sulfate, respectively and not less than 5% ammonium sulfate, =imparting a high degreeof stretch to the resultant cellulose xenthate filaments and converting the stretched cellulose "xantl ate ,yarn to regenerated cellulose.

13. A 'co'a-gulating bath for :viscose comprised or "at'least'fi .each of aborateand. asulfate calculated asborax and sodium sulfate-respectively, and maintained at alpHrldfl from:3-.0 t0 .9v0.

-14. A coagulating bath :in .accordance with claim 'l3eheated to a vtemperature:of'45":130'75" C.

'15. 4A- coagulating bath. for viscose comprised of .at-lleast 10% each of aborate and-a sulfate calculated as :boraxand sodium sulfate, respectivly, and maintainedata pH of from 3.0-to'9.0.

16. A coagulating bath for viscose comprised of at 1east.10.% borax,.at least 10%s0dium sulfate and at least 5% ammonium sulfate and maintained at.a...pH cf-from 3.0 1209.0.

1'7. A coagulating-bath for viscose comprised of at. least 10% iborax and at least 5% ammonium sulfate andmaintainedat apHof from 3.0 to-9.0.

WESTON ANDREW HARE. .FRANK'KERR SIGNAIGO.

.No references cited. 

1. A PROCESS WHICH COMPRISES PRECIPITATING VISCOSE IN AN AQUEOUS BATH HAVING A PH OF 3.0 TO 9.0 AND CONTAINING DISSOLVED THEREIN SALTS IN SUCH AN AMOUNT AS TO RAPIDLY COAGULATE THE VISCOSE WITHOUT SUBSTANTIALLY REGENERATING THE COAGULATED CELLULOSE XANTHATE, A PORTION OF SAID SALTS BEING A BORATE PRESENT IN AMOUNTS EQUIVALENT TO AT LEAST 5% BORAX. 